This proposal is submitted in response to the alarming rates of HIV among young African American men who have sex with men (MSM). The CDC recently reported that between 2006 and 2009, HIV incidence was stable among all populations in the US except young MSM. The overall increase in incidence among young MSM was driven by a 48% increase in HIV infections among young African American MSM. The broad, long-term objective of this research is to identify strategies to reduce the rates of HIV in young African American MSM. This research will take advantage of the men's avid use of mobile phone technology to deliver an innovative intervention to change their sexual risk behavior. The Specific Aims are to: 1) develop an interactive mobile phone-based HIV/STI risk-reduction intervention that is acceptable and feasible to be implemented with African American MSM ages 18 to 24 years; 2) develop an acceptable and feasible text-messaging adjunctive strategy designed to increase its efficacy; 3) pilot test the efficacy of the HIV/STI risk-reductio intervention compared with an attention-control intervention in increasing the proportion of men who report consistent condom use during anal and vaginal intercourse; and 4) pilot test whether the efficacy of the HIV/STI risk-reduction compared with the control intervention is enhanced among men randomized to the tailored text-messaging adjunctive intervention as compared with other men. African American men ages 18 to 24 years who report having anal intercourse with a man in the 2 months prior to screening will be eligible to participate. The intervention and adjunctive strategy will be developed using an iterative process involving focus groups, input from a community advisory board, usability testing, and small-scale pilot testing. Evidence of potential efficacy will be based on a pilot randomized controlled trial involving 180 men with 6-month follow-up. Men will be randomly assigned to the HIV/STI risk-reduction or an attention-control intervention. In addition, they will be randomly assigned to receive or not receive intervention-specific, individually tailored text messages. The approach draws on social cognitive theory and the applicant's Preliminary Studies with the target population. Self-reported consistent condom use, other sexual behaviors, HIV testing, and variables hypothesized to mediate intervention efficacy will be collected via audio-computer-assisted self-interviewing. The use of a mobile phone technology for intervention would allay participants' concerns about revealing their sexual involvement with men by virtue of participating in a group or workshop intervention. If current trends in smartphone use continue, this research has the potential to produce a cost-effective intervention that local, state, or national organizations might offer to their young African American MSM clients. The proposed research has great public health significance because although young African American MSM have some of the highest rates of HIV in the US, there is a paucity of efficacious HIV/STI interventions tailored to them.